Parámetros reproductivos de las poblaciones de Opisthonema libertate (Günther) (Pisces:Clupeidae) y discusión sobre su evaluación por producción de huevos, en Bahía Magdalena, B.C. Sur, México

Abstract

The reproductive period of the Pacific thread herring (Opisthonema libertate) (Günther) fishery in Bahía Magdalena Baja California ranges from March to October. The maximum spawning activity for 1982 and 1984 was observed during the months of July-September. In 1983, however, this period was somewhat prolonged apparently associated a thermal ocean anomaly “El Niño”. Histological analysis shows postovulatory follicles larger than those described for Engraulis mordax; a unique morphological structure of the ovary was observed in each catch that was sampled, this observation suggests that the reabsortion of the postovulatores follicles takes place in a very short period (approximately 24 hrs.). Consequently, the spawning frequency becomes very high as compared to that of other clupeid species of tropical waters. The mean partial fecundity was obtained from fish ovaries which under the histological analysis showed the gonads to be mature (as assessed by the presence of yolk globules). It was not possible to obtain this estimate from hydrated females because the frequency they were observed with, was very low (0.8% of the totality of sampled organisms). Thus a figure of 62,558 ovocites/female was determined as mean partial fecundity and 652.196 ovocites/gr. of female as relative fecundity. A discussion on the application of the egg production method on the evaluation of O. libertate is presented.